1. Field of the Invention
The present invention relates to medical devices. Specifically, the invention relates to inserting medical devices into a patient where the medical devices may be used in conjunction with magnetic resonance imaging.
2. Background of the Invention
An introducer is a secondary medical device that may be used in a surgical procedure to move a primary medical device into the patient. The introducer may be attached to a third device called a trajectory guide that positions the introducer in the direction of the area to be explored in the patient. The primary medical device may include, but is not limited to: a catheter with drug delivery capability; a tissue removal instrument such as a laser; an instrument for attaching an electrode; etc.
The alignment of an introducer may be controlled relative to the patient by the trajectory guide. Movement of the primary medical device relative to the patient is restricted once the introducer has been aligned. A translation range of motion of the introducer in operation is generally fixed in two coordinate axes, and limited to linear motion along one axis, into the patient. The introducer controls the linear motion along this single axis.
An introducer is used primarily in procedures where precise location of the primary medical device is critical, for example, brain surgery. Different variations of introducers are currently being used for procedures such as neurosurgery.
Typically, the patient is prepared by first fixing the patient in a location on an operating table surface. Conventionally, the skull of the patient is fixed to the table in order to keep the brain located relative to the operating table surface. A trajectory guide is then conventionally mounted to a fixture on the operating table. The patient may then be operated on directly, or the patient may be positioned in a magnetic resonance imaging (MRI) station such as a long bore MR scanner. An MR tube is used in cases where a focused area of the brain is to be imaged during the surgery. Next an opening in the skull is made, and the trajectory guide is aligned with the area of the brain to be explored.
Using one prior variation, the introducer is then attached to the trajectory guide, and the desired primary medical device is attached to the introducer. The first variation introducer includes a stepper motor, controlled by a computer, that drives the primary medical device into the patient. However, the stepper motor variation is relatively heavy and expensive. The weight of the unit requires a substantial support frame attached to the operating table to ensure that this introducer does not move during the procedure. Additionally, time consumed in re-sterilization between procedures means that this variation is frequently not available for use. The stepper motor variation is also not compatible with an MR tube environment.
A method that can be used in conjunction with an MR tube environment is “free-hand” introduction. Unfortunately, with this method, the surgeon cannot view the patient and the primary medical device in “real time.” This is because the surgeon cannot simultaneously both view the MR display screen and operate the introducer. In real time imaging, the patient is inside an MR scanner, such as a long bore MR scanner. In order to view the MR image of the patient, the surgeon must be outside the long bore MR scanner, looking at the display screen. At the same time, in order to introduce the primary medical device, the surgeon must be near the patient, and not in a position to adequately view the display screen.
A variation of introducer that has been used to overcome the real time imaging insertion problem uses hydraulic lines to remotely control the introducer. The setup of the patient in this variation is the same, but the introducer further includes a remote actuation unit and hydraulic lines that lead from the remote actuation unit to the introducer. With the hydraulic variation, the surgeon can view the patient within the long bore MR tube, and at the same time the surgeon can actuate the introducer to move the primary medical device into the patient.
A significant problem with the hydraulic introducer is that this device is expensive and contains many complicated components that must be inspected and maintained. Another problem with the hydraulic variation is that the hydraulic fluid used to actuate this variation of remote introducer must be sealed and sterile or it must be re-sterilized after each surgical procedure.
What is needed is an inexpensive, lightweight introducer that can be used once and disposed of. What is also needed is an inexpensive introducer device that requires a minimal number of components to maintain, and requires minimal patient set up equipment to further minimize costs. What is also needed is an inexpensive remote introducer that allows the surgeon to both view the patient in real time, and actuate the remote introducer to move the primary medical device into the patient.